Crimping apparatus



June 14,

W. B. M CASKILL CRIMPING APPARATUS Filed Jan. 28, 1964 INVENTOR WILLIAMBRAND MC CASKILL ATTORNEY United States Patent M 3,255,507 CRIMPINGAPPARATUS William Brand McCaskiil, Waynesboro, Va., assignor to E. I. duPont de Nemours and Company, Wilmington, Del., a corporation of DelawareFiled Jan. 28, 1964, Ser. No. 340,636 4 Claims. (Cl. 28-1) Thisinvention relates to apparatus for crimping synthetic textile fibers. Itis more particularly concerned with a modification of the stuflcn'boxcrimper to improve tow uniformity and quality.

The stutter-box crimper is commonly used to impart crimp to filaments inthe form of a tow. The tow will usually have a total denier of severalhundred thousand. Such a large mass of fibers is diflicult to crimpuniformly. It is a common practice to fold the edges of the tow so thatthe edges at crimping will be as thick as or thicker than the centralportion. It is necessary to do this so that the crimper rolls will beable to grab the edges of the ribbon bundle and force them along withthe center portion of the bundle into the crimper box. If the edges ofthe ribbon bundle are thin, they flutter and eventually break out at thecrimper rolls causing machine wraps. However, special equipment isrequired to turn in the edges of the tow ribbon. Furthermore, the amountof edge fold will sometimes vary and the thickness of the edge will notbe constant. This is apt to give trouble in processing the crimped tow.

Thus, after the crimping process, the tow may be cut into staple lengthfiber or it may be converted directly into yarn by stretch-breaking onthe Turbo Stapler and the Hood Doubler and drafting on pin drafters. Ineither case, however, it is essential that the fiber should have auniform tow thickness and should be free of damaged fibers. Non-uniformtow is diflicult to process on the Turbo Stapler, and heavy.selvages'result in Turbo Stapler breaks and slu-bby sliver. Unevennessin the tow and heavy selvages also result in non-uniform heating at theTurbo heater plates.

It is accordingly an object of this invention to eliminate the necessityof folding over the edges of the tow and to make possible the productionof crimped tow with no heavy selvages.

Other objects and achievements of this invention will become apparent asthe description proceeds.

These results are obtained in this invention by making the feed rolls ofthe stutter-box crimper slightly thinner along the major portion oftheir length, from the midpoint of each roll outward, compared to thediameter of the roll in its end regions. In other words, the rolls areshaped to leave an oblong gap between the rolls, extending along theirnip line and being wider in the central region of said nip line than atits edges. For further details in this repect, reference is now made tothe accompanying drawings, in which:

FIG. I is a top view of a pair of feed rolls with a lenticular spacebetween them along their nip line, both spacing and curvature beingexaggerated for easy visual perception.

FIG. II is a vertical section through the upper half of one roll, tobring out clearly the construction of the operating edge.

FIG. III is a similar vertical section, but showing a modified outlinefor the roll surface.

FIG. IV is a vertical diagrammatic view of a crimper provided withimproved feed rolls according to this invention.

Taking up now the drawing in detail, FIG. IV shows a conventionalstutter-box crimper, for instance, of the type described in U.S. P.2,747,233. In brief outline,

this device comprises a stuffing box 1 and feed rolls 2, 2, through thenip of which tow 3 is continuously forced into the vertical chamber 10formed by sidewalls 11, 11 and front and rear walls 12 of the stuffingbox. Except when tow is passing therebetween, the two rolls are keptnearly in contact with each other by the action of a spring-and-leverarrangement and stops (not shown). One of the sidewalls 11 terminatesshort of the bottom of the vertical chamber and is provided at its lowerend with a hinged leg or clapper device 13 which is pressed inwardsagainst the packed tow by a counterweight hung at 14. When the pressureof the crimped fiber inside the chamber overcomes the force of thecounterweight, leg 13 yields and part of the tow is discharged into acontainer.

In the present invention, the rolls 2, 2 are shaped to form an oblongand narrow gap in the central region, which gap however, is wider in itsmid-region than at its edges. Flat shoulders 25, 25 may be provided atthe extreme edges of the rolls, but these are not essential. Betweenthese shoulders (if any are provided), the roll cylinder is made ofsmaller diameter than at the shoulders. The amount of depression is notgreat. It certainly should not be made so great as to permit the tow tobe fed in without much pressure crosswise of its plane, since tractionbetween roll surface and tow is essential to compel the tow to enter thecrowded chamer below. Oust-omarily, the depth y (FIGS. II and III) willbe of the order of a few thousandths of an inch. As a generalproposition, however, the value of y may be related to the denierdistribution of the tow lengthwise of the rolls. For instance, ifthe'tow comprises 470,000 deniers and the length of the rolls is 2.5inches, and if allowance is made for the shoulder por- H tions at theedges of the rolls and for the-thinner edges of the tow itself, anaverage distribution of about.200,000 denier per inch of roll length isobtained. Accordingly, the value ofy can be defined as being from about0.0007 to 0.0030 inch for each 100,000 den/inch of average towdistribution.

The total width of the gap between the rolls, in the midregion, will, ofcourse, be 2y plus whatever additional separation is found desirablebetween the rolls. For instance, in practice with the hitherto standard(straight edged) rolls, it has been found possible to control the natureof the crimp obtained by the degree of separation between the rolls. Fora herringbone crimp, for instance, a separation of 0.017 to 0.022" hasbeen found best. With the rolls of the present invention, the distancebetween roll axes will be adjusted so that the -total separation betweenthem (inclusive of the quantity 2y) shall fall within the same range, atleast in the midregions of the length of the nip.

The length of the gap is equal to the width of the rolls, whethershoulders are provided or not, for, as said above, the rolls aregenerally kept from actual contact with each other at any point. Thefunction of the shoulders is merely to eliminate sharp edges at theextreme ends of the roll. Accordingly, their width is not critical andis preferably kept small. For instance each shoulder may be given :awidth from 1 to 5% of the total width of the roll, with the length ofthe gap therebetween being from about to 98% of the width of saidrolls.

The actual shape of the gap is not critical. In FIG. H it is shown to beof a continuously curving shape 20, resembling the outline of a convexoptical lens. In FIG. III, on the other hand, the edge of the gap isessentially saucer shaped, that is, flat at the center, as at 21, andsloping at 22, 22 toward the shoulders 25 at the edge portions. Betweenthese two extremes, many intermediate shapes are possible.

The section of FIG. III would seem most fitting for a tow which is madeup of laterally overlapping ribbons (as shown at 3 in FIG. I), andwhich, accordingly, is of essentially uniform thickness throughoutexcept at the extreme edges where only a single ribbon thickness exists.It will be noted, incidentally, that the representation of the stackingof tow 3 in FIG. I along a slanting line is merely conventional ordiagrammatic, since in actual practice the width dimension of the towwill be parallel to the axes of the two rolls. The separation betweenthe two rolls in FIG. I is likewise diagrammatic and exaggerated. Asalready mentioned, the edges of the rolls in the nip line are preferablyin tight contact with the tow at all points of its width, including theextreme edges.

In a saucer shaped design as in FIG. III, it is recommended, a practicalguide, to make the flat central portion over 70 to 85% of the width ofeach roll (length of the gap); each rising portion about 10 to 6.5%, andeach shoulder portion from 5 to 1% of the roll width.

In actual tests with this invention, good results have been obtainedwith a lenticular model whose characteristic dimensions were as follows:

Diam. of roll=4 in.; max. depression, 3 :0.002 to 0.003

1n. Width of roll=2.5 in.; width of each shoulder=0.03 to The advantagesof this invention will now be readily apparent. The use of the concavecrimper rolls of this invention results in tows that are free fromnon-uniform edges folds and heavy selvages. It also eliminates theequipment used to fold over the edges of the tow. Tows produced by useof the concave rollers are relatively free of splits and process well onthe Turbo Stapler.

The details of the above description are susceptible of wide variationand modification, within the skill of those engaged in this art. Forinstance, there is no need for undercutting both rolls to the samedepth. Any other distribution yielding a total gap between the rollsequal to 2y (if the rolls are put in contact with each other) willoperate in the same manner. As a matter of fact, the entire depth of 2ymay be cut out in just one of the rolls, leaving the other one with thehitherto standard straight edge.

I claim as my invention:

1. A crimper for synthetic textile tow, comprising in combination astuffing box and a pair of oppositely revolving cylindrical feed rollsin parallel alignment and in near contact with each other, whereby tosqueeze into the stuffing box a continuous textile tow when one ispassed through the nip therebetween, at least one of said rolls beingshaped along its outer, cylindrical surface to be slightly thinner inthe midportions thereof compared to its extreme edges, whereby toprovide a gap between the rolls whose width is narrower at its ends thanin the midregions thereof.

2. A crimper as in claim 1, said rolls being shaped to possessoppositely facing narrow shoulders at each edge, and to form a crosswisenarrow, longitudinal gap between said shoulders, the length of said gapbeing from about 90 to 98% of the width of said rolls, and the largestwidth of said gap, if said rolls are put in contact with each other,being between 0.0015 and 0.0060 for each 100,000 denier per inch in theintended average distribution of said tow along the width of said rolls.

3. A crimper having rolls as in claim 2, said narrow gap being of anessentially uniform width extending on each side of the midpoint of thecylinders for a total length equal to between :and of the length of saidgap and narrowing down from there on gradually outward until the gapreaches the region of said juxtaposed shoulders.

4. A crimper having rolls as in claim 2, said narrow gap being of anessentially double-convex lenticular shape.

References Cited by the Examiner UNITED STATES PATENTS 1,164,629 12/1915Bergman .a 226189 2,747,233 5/1956 Hitt 1966 3,145,429 8/1964 Resor19-457 FOREIGN PATENTS 835,176 9/1938 France.

DONALD W. PARKER, Primary Examiner.

L. K. RIMRODT, Assistant Examiner.

1. A CRIMPER FOR SYNTHETIC TEXTILE TOW, COMPRISING IN COMBINATION ASTUFFING BOX AND A PAIR OF OPPOSITLY REVOLVING CYLINDRICAL FEED ROLLS INPARALLEL ALIGNMENT AND IN NEAR CONTACT WITH EACH OTHER, WHEREBY TOSQUEEZE INTO THE STUFFING BOX, A CONTINUOUS TEXTILE TOW WHEN ONE ISPASSED THROUGH THE NIP THEREBETWEEN, AT LEAST ONE OF SAID ROLLS BEINGSHAPED ALONG ITS OUTER, CYLINDRICAL SURFACE TO BE SLIGHTLY THINNER INTHE MIDPORTIONS THEREOF COMPARED TO ITS EXTREME EDGES, WHEREBY TOPROVIDE A GAP BETWEEN THE ROLLS WHOSE WIDTH IS NARROWER AT ITS ENDS THANIN THE MIDREGIONS THEREOF.